BOX issues Area Forecast Discussion (AFD) at Oct 4, 7:54 PM EDT
654
FXUS61 KBOX 042354
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
754 PM EDT Sun Oct 4 2026
.WHAT HAS CHANGED...
No significant changes to the forecast.
&&
.KEY MESSAGES...
- Scattered showers this afternoon into early morning Monday.
- A sharp temperature drop is then expected for the start of the
week followed by a return to dry, fall-like conditions.
&&
.DISCUSSION...
KEY MESSAGE 1...Scattered showers this afternoon into early
morning Monday.
High pressure south of the Maritimes no longer had enough
influence to prevent clouds and scattered showers from
overspreading southern New England this afternoon. The trend of
the latest guidance suite was slightly farther south, quite
close to the 40N/70W benchmark just after midnight. Based on
this, kept the highest rainfall chances towards the Cape and
islands, while simultaneously lowering those chances farther
inland. Thinking there should be a rather sharp gradient on the
northwest edge of this storm, but there is lower confidence on
where exactly that will be. Overall, rainfall totals should
remain less than one half inch across the Cape and islands, and
generally less than one quarter inch north and west of the Cape
Cod Canal.
Thinking that most of the showers will be well offshore shortly
after midnight, and even past the southern New England coastal
waters around daybreak Monday.
KEY MESSAGE 2...A sharp temperature drop is then expected for
the start of the week followed by a return to dry, fall-like
conditions.
A deep low continues tracking eastward across Quebec to start
the week, with latest guidance indicating the 540dam thickness
line reaching northern New England, generally across Maine at
its southernmost pass. The 560dam thickness line may extend
through central MA. High pressure follows this low, which will
aid in drying out the region and remains the main story for this
week.
With the passage of this low, colder, drier Canadian air will
plunge south, with 850 mb temperatures reaching 0C and lower
across the higher elevations late Monday night/early Tuesday
morning. 925 mb temperatures may also approach 0C in these same
areas and generally remain below 10C through Tuesday night as
well. This environment will be supportive of lows Monday night
in the low 40s and upper 30s. Tuesday night looks to be cooler
given some radiational effects possible with diminishing winds
overnight and clear skies as another high pressure passes just
to the south of southern New England.
The flow aloft shifts more WSW to SW as the low exits and high
pressure centered to our south midweek tracks east. With the
return of SW flow and drier conditions, more seasonable
temperatures take hold for the back half of the week. Ensembles
also hint at the chance of high temperatures getting back to the
low 70s towards Thursday afternoon, generally across the CT
Valley, Merrimack Valley, and the coastal plain. Probabilities
currently range between 20 and 60 percent, with the highest
probabilities in the GEFS and lowest in the ECMWF ensemble.
Overall, though, highs are expected to be more so in the 60s for
the second half of the week into the weekend.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight...High confidence in trends, moderate confidence in
timing of showers.
MVFR with pockets of VFR early, then degrading to IFR over SE
MA, RI, and the Islands overnight with showers. Lowered
visibilities more likely over ACK and Cape terminals tonight
where scattered showers should persist through around 05z-06z
tonight. VFR expected to persist west of a line from BOS-PVD-
WST, outside of some brief MVFR early for BOS and ORH this
evening. Winds become light to calm.
Monday and Monday Night...High confidence.
Lingering IFR across the Cape and Islands Monday morning.
Otherwise, VFR. Gusty W to WNW winds developing by early
afternoon. Gusts should diminish towards sunset with skies
clearing, though breezy WNW winds continue at 5-15 kt overnight.
KBOS Terminal...High confidence in trends, moderate confidence
in timing. MVFR not expected to last very long outside of the
00z-03z timeframe this evening, though it could fluctuate
between SCT/BKN.
KBDL Terminal...High confidence in TAF.
Outlook /Tuesday through Friday/...
Tuesday: VFR. Breezy.
Tuesday Night: VFR.
Wednesday through Thursday: VFR. Breezy.
Thursday Night through Friday: VFR.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through Monday Night...High confidence.
A low pressure passes southeast of the waters tonight, with
another cold front to pass by during Monday. Widespread showers
tonight, especially across the southern waters. Gusty west winds
then develop with the frontal passage Monday afternoon. Posted
Small Craft Advisories for marginal wind gusts up to 25 kt. In
addition, seas should build to 5-7 feet across the outer coastal
waters.
Outlook /Tuesday through Friday/...
Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft.
Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Wednesday: Winds less than 25 kt.
Wednesday Night: Winds less than 25 kt. Seas locally
approaching 5 ft.
Thursday through Friday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 9 PM Monday to 1 AM EDT Tuesday for
ANZ232.
Small Craft Advisory from 10 AM Monday to 1 PM EDT Tuesday for
ANZ250.
Small Craft Advisory from 8 AM Monday to 1 PM EDT Tuesday for
ANZ254.
Small Craft Advisory from 3 PM Monday to 1 PM EDT Tuesday for
ANZ255-256.
&&
$$
DISCUSSION...Belk/Hrencecin
AVIATION...Belk/Hrencecin
MARINE...Belk/Hrencecin
Source: BOX issues Area Forecast Discussion (AFD) at Oct 4, 7:54 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202610042354-KBOX-FXUS61-AFDBOX)
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